After this open your items_control.txt you will set here the item you want to sell

(item name) (minimum) (auto-store) (auto-sell) [put in cart] [get from cart]
item name : Name of the item.
miminum : The minimum amount of this item that you want to keep in inventory.
autostore : Set to 1 to walk back to a Kapra NPC to put in storage.
autosell : Set to 1 to sell item at a buy/sell NPC.
put in cart : Set to 1 to automatically put this item in cart.
get from cart : Set to 1 to automatically get this item from cart.

For example

If you want to store Jellopy just type Jellopy 0 1 0

If you want to store all the item in your invertory just typeall 0 1 0